In the operation of vending machines and other coin operated machines, coins are inserted into a slot and then travel through a runway to a coin validator, acceptor or other type of coin mechanism. The coin validator determines whether the coin is genuine, and if so the coin is routed to a collection box or stack. Coins can sometimes stick in the coin runway before reaching the coin mechanism. Furthermore, coin operated machines are subject to vandalism. One form of fraud is to attach a string to a coin, insert the coin into the slot and, after activation of the coin mechanism, withdraw the coin from the vending machine.
In the operation of a damage- and debris-free coin runway, inserted coins travel to the coin mechanism within a set time or tolerance range. If a coin becomes jammed in the coin runway due to either debris or a fraud attempt, the coin will either never arrive at the coin mechanism or take longer to reach the coin mechanism than expected. The vending machine may become inoperable and may require maintenance. It is desirable to have a coin operated machine that will detect coin jams and tampering.